1. Technical Field
The present invention relates to a method of producing a fermentation product from a composite material. More particularly, the present invention relates to a method of producing ethanol from a composite material derived from municipal solid waste.
2. Background Art
By far the most common method of solid waste disposal in the United States is the landfill followed by incineration while composting of solid wastes accounts for only an insignificant amount.
In modern landfills, the refuse is spread in thin layers, each of which is compacted by heavy industrial equipment before the next layer is spread. When about ten feet of refuse has been deposited, it is covered by a thin layer of clean earth which also is compacted. Pollution of surface and groundwater is believed to be minimized by lining and contouring the fill, compacting and planting the cover, selecting proper soil, diverting upland drainage, and placing wastes in sites not subject to flooding or high groundwater levels.
Land-filling does pose many problems and concerns, including rising landfill maintenance and development costs, decreasing availability of landfill sites, and an increasing risk that substances leaching from landfills may contaminate groundwater and surface water. Landfills are also known to generate flammable gases through the anaerobic decomposition of the organic solid waste and thus proper venting and burning of the gases is often necessary to eliminate or alleviate potentially dangerous conditions.
Sanitary landfills were considered the cheapest most satisfactory means of disposal, but only if suitable land was available for use within an “economic range” of the source of the wastes (i.e., geographic proximity making waste removal and hauling economically feasible), because collection and transportation costs are known to account for seventy-five percent of the total cost of solid waste disposal and management.
A growing trend associated with the treatment and handling of solid waste material is “resource recovery”. Resource recovery is intended to recover useful materials from raw municipal solid waste. The handling of such wastes may include preprocessing the municipal solid waste with grinding or shredding machines, magnetic separators, air classification that separates the light and heavy fractions, screening, and/or washing. Resource recovery methods, therefore, attempt to reduce (i.e., recycle) the solid waste into a more manageable, although not always useful form, but such methods are known to be quite costly.
One type resource recovery method is the conversion of waste into energy, either directly or indirectly. Historically, the most common conversion method of waste into energy has been the incineration of the waste material. However, this method of recovering energy is becoming less and less feasible due to both the cost and environmental constraints. Additionally, the increasing stringency of air emission standards as well as the public health concerns have influenced industry to create different technologies for the conversion of municipal waste into energy.
Other methods of waste-to-energy conversion including the preparation of a fuel source material from the waste product. For example, U.S. Pat. No. 5,135,861 issued to Pavilon, discloses the production of anhydrous ethyl alcohol from a quantity of biomass. The carbon dioxide acquired from the fermentation process of the biomass is utilized to hydrolyze additional biomass for fermentation into ethyl alcohol.
Draanen et al. (U.S. Pat. No. 5,932,456) claims a method of fermenting biomass to produce either ethanol or other fermentation products including citric acid and isopropanol. The '456 patent preferably uses the microorganism Zymomonas mobilis for the fermentation of biomass and solid waste and demolition debris.
U.S. Pat. No. 5,104,419, issued to Funk, describes a method of producing a liquid fuel such as methanol from a waste source such as solid municipal waste. The process includes partially oxidizing and combusting the solid waste material under high temperatures as well as gas separation techniques to produce a liquid fuel source from the waste material.
Most commonly the conversion of waste into energy is an indirect process wherein liquid ethanol is produced. Ethanol is a flammable, colorless chemical compound with the formula C2H5OH. Currently the largest single use of ethanol is for motor fuel and fuel additives. Thus far, the United States fuel ethanol industry is largely based on the fermentation of corn byproducts. With its current capacity well over 10 billion liters annually, the need for producing ethanol will continue to grow significantly as the Energy Policy Act of 2005 requires U.S. fuel ethanol production to increase to at least 7.5 billion gallons by the year 2012. Furthermore, ethanol is also used in the production of biodiesel so long as the ethanol has a water content of less than 2%. The ethanol replaces the much more toxic alcohol, methanol, providing for a safer way to produce biodiesel.
In addition to the fuel industry, ethanol is also used in the production of other chemical compounds such as ethylene and butadiene. Even further, ethanol can be used to make ethylamines which are commonly used in the synthesis of pharmaceutical compounds.
Until now, drawbacks associated with the conversion of waste materials to energy have included the inconsistency of the starting material as well as the achievement of a conversion rate of municipal solid waste to energy which is economically feasible.
It is believed that a specific composite material will remedy these concerns while providing for a sufficient conversion rate to a liquid fuel.
The composite material and art to which the inventive process relates include the information of the type disclosed in U.S. Pat. No. 6,017,475 granted to Cantrell and also U.S. Patent Application No. 2004/0080072 of Bouldin et al. which are incorporated by reference and are fully set forth herein. Notably, the '072 application is directed to a process of deriving a composite material from municipal solid waste.
What is desired, therefore, is a method for efficiently making ethanol from a composite material derived from municipal solid waste wherein the overall conversion from waste to ethanol is sufficiently efficient and also economically viable.